PROJECT SUMMARY/ABSTRACT Oral cancer patients suffer from pain with impaired oral function. Oral cancer pain is initiated and maintained in the periphery and worsens during cancer progression. Perineural invasion (PNI), defined as cancer invading in, around, or along the nerve, correlates with increased pain severity and poor prognosis. Treatment options for pain are limited. No targeted treatments for PNI exist. Current research on oral cancer pain mainly focuses on the effect of cancer mediators on primary afferent neurons. Neuropathic pain caused by PNI is rarely addressed mechanistically. The role of Schwann cells (SCs), the most prevalent cell type supporting peripheral nerves, has not been defined in oral cancer PNI and pain. We found that oral cancer induces SC activation, a well-known response of SCs to nerve injury. Oral cancer cells and SCs mutually promote proliferation, migration, and invasion. Supernatant from oral cancer-activated SCs induces nociceptive behaviors in mice. We found that oral cancer cells are enriched with the soluble form of tumor necrosis factor (sTNF), a master regular of cytokines. sTNF is known to activate SCs and mediates neuropathic pain. The primary receptor for sTNF is TNFR1. We hypothesize that sTNF activates SCs through TNFR1 to promote oral cancer PNI and neuropathic pain. Our hypothesis is based on our observations in patients, cell culture and animal models of oral cancer and PNI. This proposal will combine expertise from oncology, pathology, electrophysiology, cell biology, nerve ultrastructure, animal behavior, and statistics to: Aim 1. Evaluate associations between SC activation, SC TNFR1 expression, PNI, and pain in human oral cancer. Aim 2. Characterize the effect of sTNF neutralization or SC TNFR1 gene deletion on oral cancer pain. We will determine whether sTNF-TNFR1 mediates SC activation, which causes SCs to release nociceptive mediators, and/or is accompanied by myelin/axon abnormalities, resulting in nociceptor hypersensitivity and neuropathic pain. Aim 3. Characterize the effect of sTNF neutralization or SC TNFR1 gene deletion on oral cancer PNI. We will test whether sTNF- TNFR1 mediated SC activation facilitates proliferation, migration, and invasiveness between SCs and oral cancer cells, promoting PNI. Our objective is to elucidate the mechanism of SC activation and to test the therapeutic potential of controlling SC activation to reduce oral cancer PNI and pain. Understanding how SCs contribute to oral cancer PNI and neuropathic pain may reveal new opportunities and strategies to interrupt these co-morbidities of oral cancer.